This invention relates to improvements in rubber-to-metal bonding. More particularly, the invention is directed to using a mixture comprised of epoxidized diene polymer and methylolated phenolic resins as a primer in rubber-to-metal bonding operations.
In the adhesive bonding of rubber to metal, a primer is usually required so as to insure the formation of a strong adhesive bond. Furthermore, in many applications the primers must also be flexible to accommodate metal forming operations without loss of metal to primer adhesion, resistance to corrosion, thermal or chemical degradation and anodic or cathodic deterioration. In formulating primer compositions which possess the foregoing properties, the formulator must also consider the requirement that the primer must not only form a strong adhesive bond with the final or cover coating but also enhance the bonding between the adhesive and the metal.
Many structural parts utilized in various industrial applications contain rubber-to-metal adhesive bonds. One example of an industrial application which utilizes metal parts bonded to rubber substrates can be found in the automobile industry where fluid-filled engine mounting devices are used to mount engines to automobile frames in order to isolate engine vibration. The mounting devices employ rubber-to-metal bonds which are exposed to fluids such as ethylene glycol. At the increasingly high temperatures being experienced in current automobile engines, many of the traditional rubber-to-metal adhesives utilized in the mounting devices are exhibiting deterioration and unacceptable flexibility in these high temperature fluid environments.
It is an object of the invention, therefore, to bond rubber-to-metal substrates using a primer composition which after cover coating provides a bonded rubber-to-metal article of manufacture exhibiting outstanding flexibility and bonding properties.
Another object of the invention is to provide a rubber-to-metal adhesively-bonded assembly whose adhesive bonds exhibit strong resistance to corrosion, heat, humidity and chemicals such as ethylene glycol/water systems.